L6738A STMicroelectronics, L6738A Datasheet
L6738A
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L6738A Summary of contents
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... The oscillator is programmable up to 600 kHz. The L6738A provides a programmable overcurrent protection and overvoltage protection. The current information is monitored across the inductor DCR. The L6738A is available in a VFQFPN 16 3x3 mm package. Table 1. Order code L6738A L6738A as low as 1.5V ...
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... Overcurrent threshold setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 7 Main oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 8 High Current embedded drivers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 8.1 Boot capacitor design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 8.2 Power dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 9 Application details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 9.1 Compensation network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 9.2 Layout guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 10 Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 10.1 Inductor design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 10.2 Output capacitor( 2/32 Doc ID 18134 Rev 1 L6738A ...
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... L6738A 10.3 Input capacitors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 11 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 12 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 Doc ID 18134 Rev 1 Contents 3/32 ...
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... List of tables List of tables Table 1. Device summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Table 2. Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Table 3. Thermal data Table 4. Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Table 5. Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Table 6. L6738A protection at a glance Table 7. Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 4/32 Doc ID 18134 Rev 1 L6738A ...
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... L6738A List of figures Figure 1. Typical application circuit (fast protections Figure 2. Typical application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Figure 3. Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Figure 4. Pin connection (top view Figure 5. LS-less startup (left) vs. non-LS-less startup (right Figure 6. Current reading network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Figure 7. ROSC vs. switching frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Figure 8. Bootstrap capacitor design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Figure 9. ...
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... Application circuit Figure 1. Typical application circuit (fast protections 12V CC R OSC OSC PGOOD PGOOD EN EN COMP FBG I L6738A Reference Schematic 6/32 C DEC GND VCC C DEC VCCDR BOOT UGATE HS PHASE LGATE CSP CSN VSEN Doc ID 18134 Rev 1.5V to 19V BULK OUT C ...
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... L6738A Figure 2. Typical application circuit 12V CC R OSC OSC PGOOD PGOOD EN EN COMP FBG I L6738A Reference Schematic Typical application circuit and block diagram C DEC GND VCC C DEC VCCDR BOOT UGATE PHASE LGATE CSP CSN VSEN Doc ID 18134 Rev 1.5V to 19V BULK HS L ...
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... Block diagram Figure 3. Block diagram OVER CURRENT CSN CSP OCP CLOCK OSC PROGRAMMABLE OSCILLATOR EN OVP +25% UVP -25% 8/32 OVP UVP CONTROL LOGIC, MONITOR, PROTECTIONS & EFFICIENCY OPTIMIZATION PWM ERROR AMPLIFIER + 0.80V - Doc ID 18134 Rev 1 L6738A BOOT UGATE HS PHASE VCCDR LGATE LS GND L6738A ...
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... VSEN is within specifications. Pull-up to 3.3 V (typ) or lower, if not used it can be left floating. Enable Pin Pull-high to < enable conversion, 10 µA pull-down provided. Pin description and connection diagrams VCCDR 1 12 LGATE 2 11 L6738A PHASE 3 10 BOOT Function Section 8 Doc ID 18134 Rev 1 CSN ...
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... Junction temperature range J 10/32 Function - C to FB. The device cannot be disabled by grounding this pin VSEN and with Section 6 for details. Section 7 for details). If floating, the switching fre- Parameter Doc ID 18134 Rev 1 L6738A - C to COMP the SW connected OSC . OUT Value Unit 45 °C/W 1 °C/W 150 ° ...
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... L6738A 3 Electrical specifications 3.1 Absolute maximum ratings Table 4. Absolute maximum ratings Symbol GND CC, CCDR to GND PHASE BOOT UGATE to GND, VCCDR = < 200 nsec. to GND V PHASE to GND, VCCDR = < 200 nsec GND LGATE to GND, VCC < GND, VCC > CSP, CSN to GND All other pins to GND 1 ...
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... EN falling Vout to FBG (1) BOOT - PHASE = PHASE = 3.3 nF UGATE BOOT - PHASE = 12 V; 100 mA ( GND = 5.6 nF LGATE 100 mA CSP - CSN; 7x masking VSEN rising un-latch, VSEN falling VSEN falling Doc ID 18134 Rev 1 L6738A Min. Typ. Max. Unit 100 % 0.9 V 0.5 V -0.5 - 0.5 % 120 ...
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... PGOOD in a compact VFQFPN16 3x3 mm. The L6738A is designed to operate from supply. The output voltage can be precisely regulated to as low as 0.8 V with ±0.5 % accuracy over line and temperature variations ...
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... Soft-start 5 Soft-start The L6738A implements a soft-start to smoothly charge the output filter avoiding high in- rush currents to be required to the input power supply. During this phase, the device increases the internal reference from zero closed loop regulation. The soft- start is implemented only when VCC and VCCDR are above their own UVLO threshold and the EN pin is set free ...
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... L6738A Figure 5. LS-less startup (left) vs. non-LS-less startup (right) Doc ID 18134 Rev 1 Soft-start 15/32 ...
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... Output voltage setting and protections 6 Output voltage setting and protections The L6738A is capable of precisely regulating an output voltage as low as 0 fact, the device comes with a fixed 0.8 V internal reference that guarantees the output regulated voltage to be within ±0.5 % tolerance over line and temperature variations (excluding output resistor divider tolerance, when present) ...
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... DCR current sensing requires time constant matching between the inductor and the reading network: The L6738A monitors the voltage between CSP and CSN, when this voltage exceeds the OC threshold, an overcurrent is detected. The IC works in constant current mode, turning on the low-side MOSFET immediately while the OC persists and, in any case, until the next clock cycle ...
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... Output voltage setting and protections 6.2 Overcurrent threshold setting The L6738A detects OC when the difference between CSP and CSN is equal (typ). By properly designing the current reading network possible to program the OC threshold as desired (See Time constant matching is, in this case, designed considering: This means that once inductor has been chosen, the two conditions above define the proper values for R1 and R2 ...
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... L6738A 7 Main oscillator The controller embeds a programmable oscillator. The internal oscillator generates the sawtooth waveform for the PWM charging with a constant current and resetting an internal capacitor. The switching frequency, F The current delivered to the oscillator is typically 20 µA (corresponding to the free running frequency F ...
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... High Current embedded drivers The L6738A provides high-current driving control. The driver for the high-side MOSFET uses the BOOT pin for supply and the PHASE pin for return. The driver for the low-side MOSFET uses the VCCDR pin for supply and the GND pin for return. ...
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... L6738A Two main terms contribute in the device power dissipation: bias power and drivers' power. ● Device Power (P supply pins and it is simply quantifiable as follows: ● Drivers' power is the power needed by the driver to continuously switch ON and OFF the external MOSFETs function of the switching frequency and total gate charge of the selected MOSFETs ...
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... OUT / can be fixed choosing the right R 0dB /2π. To achieve a good phase margin, the control loop gain SW shows an asymptotic bode plot of a type III compensation. Doc ID 18134 Rev 1 L6738A depending on the L OUT C OUT ESR and EA output with transfer /R ratio, however, for F FB ...
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... L6738A Figure 10. Example of type III compensation. Gain [dB] open loop EA gain closed loop gain compensation gain open loop converter gain 0dB ● Open loop converter singularities ESR ● Compensation Network singularities frequencies: = ----------------------------------- - 2π = ---------------------------------------------------------- 2π place the poles and zeros of the compensation network, the following suggestions may ...
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... Check phase margin obtained (it should be greater than 45°) and repeat if necessary. 9.2 Layout guidelines The L6738A provides control functions and high current integrated drivers to implement high-current step-down DC-DC converters. In this kind of application, a good layout is very important. The first priority when placing components for these applications has to be reserved to the power section, minimizing the length of each connection and loop as much as possible ...
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... L6738A Connect output bulk capacitors (C inductance and resistance associated to the copper trace, also adding extra decoupling capacitors along the way to the load when this results in being far from the bulk capacitors bank. Remote Sense Connection must be routed as parallel nets from the FBG/VSEN pins to the load in order to avoid the pick-up of any common mode noise ...
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... Figure 13. Inductor current ripple vs. output voltage 26/32 – OUT ----------------------------- - = L ⋅ ∆ the input voltage and V IN shows the ripple current vs. the output voltage for different values of the = 5 V and Doc ID 18134 Rev 1 V OUT -------------- ⋅ the output OUT L6738A ...
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... L6738A 10.2 Output capacitor(s) The output capacitors are basic components to define the ripple voltage across the output and for the fast transient response of the power supply. They depend on the output voltage ripple requirements, as well as any output voltage deviation requirement during a load transient ...
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... The equation reaches its maximum value, I input capacitor ESR and, in the worst case, are: 28/32 ) and the duty-cycle (D) for the regulation as OUT ⋅ ⋅ – rms OUT /2, with D = 0.5. The losses depend on the OUT 2 ⋅ ( ⁄ ESR I 2 OUT Doc ID 18134 Rev 1 L6738A ...
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... L6738A 11 Package mechanical data In order to meet environmental requirements, ST offers these devices in different grades of ® ECOPACK packages, depending on their level of environmental compliance. ECOPACK specifications, grade definitions, and product status are available at www.st.com. ECOPACK registered trademark. Doc ID 18134 Rev 1 Package mechanical data 29/32 ...
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... Doc ID 18134 Rev 1 OUTLINE AND MECHANICAL DATA VFQFPN-16 (3x3x1.0mm) Very Fine Quad Flat Package No lead L6738A ...
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... L6738A 12 Revision history Table 7. Document revision history Date 03-Nov-2010 Revision 1 Initial release. Doc ID 18134 Rev 1 Revision history Changes 31/32 ...
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... Australia - Belgium - Brazil - Canada - China - Czech Republic - Finland - France - Germany - Hong Kong - India - Israel - Italy - Japan - Malaysia - Malta - Morocco - Philippines - Singapore - Spain - Sweden - Switzerland - United Kingdom - United States of America 32/32 Please Read Carefully: © 2010 STMicroelectronics - All rights reserved STMicroelectronics group of companies www.st.com Doc ID 18134 Rev 1 L6738A ...